When the Queen was pregnant with Charles, an oblique announcement said merely that she “would undertake no public engagements until June” - and left the world to figure out what that meant.

Princess Diana felt her pregnancies were too public - “The whole world is watching my stomach,” she once said.

On Monday, Kate and William put news of her pregnancy up on their website, which promptly crashed. Serious newspapers began live-blogging on the issue. TV reporters were stationed outside the hospital. Twitter buzzed with quips like “Dilatey Katie”.

Pregnant ... the Duchess of Cambridge has set off a media frenzy. Photo: Reuters

Bookies announced Elizabeth (8/1 ) and Diana (12/1) the top favourite names for a girl and Philip (14/1) and Edward (16/1) for a boy (and you can bet on the hair colour, too, 6/4 brown, 2/1 blond).

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And columnists began speculating about when, precisely, the baby might have been conceived. The holiday in France that spawned the topless pictures? Maybe, concluded one paper, though perhaps it could have been during the couple's tour of South-East Asia. Another magazine reports “insider” claims that the baby is the result of a passionate night in their rented home in Wales.

Princess Diana felt her pregnancies were too public - “The whole world is watching my stomach,” she once said - but the level of intrusion is already far greater for Kate, particularly now that details of her medical situation are known.

The news is a blessing and a curse for women's magazines around the world, which will be madly pulling scheduled covers in order to roll out (pre-prepared?) spreads on royal baby bliss and pregnancy misery. But the very illness that has made the pregnancy such hot news will later bedevil the media, as it means Kate is much more likely to spend the next seven months living a private life rather than providing joy for paparazzi. Severe pregnancy-nausea of her kind can go on for up to 14 weeks, and in rare cases can last the whole pregnancy.

The media upside: extreme pregnancy nausea is also slightly associated with a higher likelihood of twins. Princess Mary of Denmark could get a run for her money.

The royal baby-to-be means unalloyed happiness for Prime Minister David Cameron, wrestling as he was with the Leveson fall-out and welfare reform and the euro-crisis, but now likely to be revelling in the spotlight turning to what an Independent columnist has sourly dubbed “the feel-good foetus”.

The London Telegraph's Tom Chivers is doing a similar bah-humbug, saying he needs to coin a new word for what he is already feeling: “Babigue? Pregxhaustion? Ennuioetus?” Several of the Top Ten Stories Zoe Williams of the Guardian doesn't want to read are already up on newspaper websites, including advice on what Kate should and shouldn't be eating and speculation as to how Diana would have reacted.

The Queen is probably still sorting out her own reaction. She was told only as Kate was being taken to hospital. The official announcement talks of her delight. But for her and her dynasty, this is about more than an old woman's pleasure at the promise of her first great-grandchild.

William, Kate and their children are likely to become the new face of the monarchy long before they sit on thrones. It is an age where image, not monarch, is king; they are young, handsome, apparently in love, and ready objects for the projection of their subjects' longing for the fairy-tale.

The happy couple ... William and Kate. Photo: Getty Images

They also seem to have “the common touch”; friendly, approachable, down-to-earth.

The Queen has had many moments of glory. The oceanic swell of people turning out for her Jubilee was, to a non-Brit, extraordinary. But she is respected rather than loved. And, while she has kept her footing on deck during some truly stormy seas, she is like the wall-paper of Britons' lives: there, seemingly, forever, but faded now, and reminiscent of another era and its ways. The gloves alone say it all about her un-touchableness.

But before William and Kate come Charles and Camilla. A poll just after the Jubilee suggested that, for the first time, the British populace favoured a Charles and Camilla combo on the throne ahead of a William-and-Kate ensemble. Fifty-one per cent wanted Charles crowned, although a sizeable 40 per cent still favoured William. Camilla is successfully chipping away at the national resentment over Diana.

But polls on this issue do not matter a hill of beans. The monarchy is not a popularity contest. There is a queue and it will be observed, failing mischance.

And seductive as youth and beauty and cute babies may be, next year's royal arrival is just as likely as Charles to grow into a middle-aged monarch-in-waiting. According to James Kirkup on the London Telegraph, life-expectancy data suggests the child due next year would probably not succeed until 2068, when he or she was 56 years old, and might well reign into the 22nd century.

By which time he or she might also find themselves sharing the limelight with an expected grandchild who will represent the new face of the monarchy….